ios Oc保存图片为png，分享图片

//保存成png
UIImageWriteToSavedPhotosAlbum([UIImage imageWithData:UIImagePNGRepresentation(self.img)], self, @selector(image:didFinishSavingWithError:contextInfo:), (__bridge void *)self);

//默认jpg
// UIImageWriteToSavedPhotosAlbum(self.img, self, @selector(image:didFinishSavingWithError:contextInfo:), (__bridge void *)self);

//分享图片
NSArray *activityItems = @[_img];
UIActivityViewController *activityVC = [[UIActivityViewController alloc] initWithActivityItems:activityItems applicationActivities:nil];
activityVC.modalPresentationStyle = 0;
[self presentViewController:activityVC animated:YES completion:nil];